We showed you the video of a man snatching a toddler right out of a shopping cart. Now, the child's mom is speaking out. And abc's alex perez has the story. Reporter: For the first time, mom alisa keating is talking about the frightening ordeal she'll never forget. I immediately panicked. Reporter: The whole thing captured on surveillance cameras. Her 2-year-old always playful daughter, zoe, being held at knife-point, by a stranger who snatched her out of the shopping cart in front of her sister. I was frantic. Nothing can prepare you, I don't think, for a moment like this. Reporter: Keating was at this midwest oklahoma walmart. And had just stepped from the shopping cart to get steaks out of the cooler, when sammy wallace grabbed zoe. I started screaming at the top of my lungs. Help me. This man has my baby. Reporter: Wallace, a wanted felon, according to authorities, with a history of mental illness, refused to get zoe go. So, keating started pleading. I said, don't hurt my baby. We were unable to have children. For three years, I prayed for her every day that the lord would give me a child. And the lord gave her to me. Please, don't hurt her. Reporter: But wallace ignored her pleas. The surveillance shows one customer as he stepped in and tried to block him with a shopping cart. Within minutes, police arrived and got keating to safety and tried to negotiate with wallace. Even providing him a chair. That was the hardest thing to do was to leave my baby there in this man's arms. Reporter: But wallace started with a heart dropping countdown. Starting at 60, saying he would kill the girl by the time he got to zero. That's when captain david huff saw an opportunity, stepped in close, and fired at wallace, killing him, saving zoe's life. Mom says zoe was shaken up. But is already back to smiling and playing with her big sister, ashley. I've never been more thankful to have my baby. Reporter: For "good morning america," alex perez, abc news, oklahoma city.

This transcript has been automatically generated and may not be 100% accurate.

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